I cannot answer, but I can help.
You need to write this yourself. Maybe try writing it like a diary? Get creative! Some vocabulary words could be, "ventured," "sailed," "maelstrom," and "mizzen"!
An idea I thought up was to escape a threat, such as an enemy ship or a dangerous sea creature. They might have left the treasure behind because they didn't have time to take the treasure! You can use these ideas if you want!
Remember, let your creativity flow! You got this!